A combined cycle power plant uses both gas and steam turbines to generate the total plant power output. The gas turbine may be considered the primary power source. Exhaust (waste heat) from the gas turbine is used to generate steam that powers the steam turbine, which generates additional power as a secondary source. Existing systems control operation of the gas turbine, the steam turbine, or other plant subsystems to affect plant performance without considering the interrelationship between the gas turbine and the steam turbine. Further, existing systems do not consider the interrelationship between the gas turbine and the steam turbine or the overall plant operations in assessing problems or in maintaining subsystems.